A conventional art making it possible to use a plurality of phone numbers in one mobile device is known. For example, Japanese Laid-open Patent Publication No. 2005-340962 discloses a technology making it possible to use a plurality of phone numbers in one mobile device, in which the mobile device transmits terminal information and additional information of specifying the mobile device to a predetermined apparatus when the mobile device performs call origination and the predetermined apparatus performs a call request on a communications partner based on the terminal information and additional information.
Japanese Laid-open Patent Publication No. 2001-320755 discloses a technology in which a mobile device, which has a public cellular telephone function and an owned-operated cordless telephone function, receives an owned-operated area identifier of specifying an owned-operated network service area from an IC (Integrated Circuit) tag provided in the owned-operated network service area and then modifies its own phone number to a phone number corresponding to the received owned-operated area identifier with reference to an association table of owned-operated area identifiers and phone numbers previously stored in the mobile device.
The conventional arts have a problem in that a phone number to be modified should be previously set in a mobile device. In other words, when a different phone number is newly used for a mobile device, this new phone number must be set in the mobile device.
For example, when a company officially announces different phone numbers for each company department to customers, the company requires a work of causing the owner of a mobile device to register a new phone number in the mobile device or a work of collecting a mobile device from an owner to register a new phone number in the mobile device and returning the mobile device to the owner whenever the number of departments is increased or the phone number is changed.
Particularly, a company where many company employees together use phone numbers for personal and company use or a company where employee movement is frequently performed requires an enormous amount of man-hours to perform this kind of complicated work many times while carrying out thorough registration omission prevention.
Therefore, when a plurality of phone numbers is used in one mobile device, the important problem is realizing a technology for easily modifying a phone number to another phone number without previously setting the other phone number in the mobile device.